<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>搜索</title>
    <style type="text/css">
        .search {
            width: 30%;
            margin: 40px auto 20px 20px;
            display: flex;
        }

        .search input {
            float: left;
            flex: 4;
            height: 30px;
            border: 1px solid black;
            box-sizing: border-box;
            padding-left: 10px;
        }

        .search button {
            float: right;
            flex: 1;
            height: 30px;
            background-color: yellowgreen;
        }
    </style>
</head>

<body>
    <div class="search">
        <input type="text" placeholder="请输入..." name="" id="" value="" />
        <button>搜索</button>
    </div>
</body>

</html>